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Lect 17Digestive Gastrointestinal Tract Accessory Organs Intro to Anatomy, Physiology and Nutrition.

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Presentation on theme: "Lect 17Digestive Gastrointestinal Tract Accessory Organs Intro to Anatomy, Physiology and Nutrition."— Presentation transcript:

1 Lect 17Digestive Gastrointestinal Tract Accessory Organs Intro to Anatomy, Physiology and Nutrition

2 Digestive Tract = ___________ Mouth Pharynx Esophagus Stomach Small Intestine Large Intestine Anus Accessory Organs Teeth and salivary glands Liver/gall bladder Pancreas Mesenteries

3 Alimentary Canal - Characteristic Cross Section –__________ = Passage down the middle –Mucosa –Submucosa What kind of tissue? What is found in this layer? –Muscle layer –Serosa = ? Type of membrane ____________


5 Functions of the Digestive System The process of taking foods and liquid into the mouth: Ingestion The release of water, acid, buffers, and enzymes by cells and accessory organs into the lumen. Secretion Alternating contraction and relaxation of smooth muscle. Peristalsis Mixing and propulsion Mechanical and chemical break down of organic material into small molecules. Digestion

6 Mouth Cheeks: lateral walls –buccinator muscles, bucal fat pads –Non-keratinized stratified squamous epithelium –Lips attach to gum: labial frenulum (a midline fold) Vestibule: space between lips and gums (gingiva)/teeth Oral cavity proper – from gums and teeth to Fauces


8 Oral Cavity Floor: –Mylohyoid muscle –Tongue frenulum Palate: –Hard Palate: palantine bones + part of maxilla –Soft Palate: + Uvula – close oral cavity nasopharynx Tonsils: –Palatine: either side of tongue –Lingual : near base of tongue at hyoid bone –Pharyngeal: = adenoids – posterior wall of pharynx


10 Teeth Fours types: –Incisors –Canines –Premolars –Molars Primary teeth: deciduous – baby teeth Adult teeth –dental formula: number of teeth of each type in one half of each jaw reading from the front (incisors) to back (molars) Humans Adults: 2123/2123



13 Tortora & Grabowski 9/e 2000 JWS Salivary Glands Parotid below your ear and over the masseter Submandibular is under lower edge of mandible Sublingual is deep to the tongue in floor of mouth All have ducts that empty into the oral cavity

14 Pharynx – 3 regions: Nasopharynx Oropharynx Laryngopharynx Swallowing: What prevents food from entering nasal cavity: What temporarily seals oral cavity/pharynx? What closes opening to respiratory passage? Peristaltic wave pushes _______ down __________.

15 The Esophagus Anatomy –A collapsible 10 inch long muscular tube. Functions –Secrete mucus and transport food from the pharynx to the stomach. Rhythmic waves of muscle contraction? (Peristalisis). Pierces the diaphragm at hiatus –hiatal hernia or diaphragmatic hernia

16 Peritoneum visceral layer covers organs parietal layer lines the walls of body cavity Peritoneal cavity –potential space containing a bit of serous fluid

17 Greater Omentum- fatty apron: covers transverse colon and small intestine.

18 Falciform Ligament: Suspends liver from anterior wall of abdomen/diaphragm Lesser Omentum: suspends stomach and duodenum from liver Mesentary Proper: Extends from dorsal wall of abdominal cavity, suspends small intestine Mesocolon: binds transverse and sigmoid colon to dorsal abd. wall

19 Falciform Ligament Lesser Omentum Greater Omentum Mesentary Proper Mesocolon

20 Which side is it on? Size when empty? Parts of stomach? Structure of its walls? Smooth muscle layers rugae Gastric pits What digestive processes occur here Associated mesenteries? Semifluid contents are known as?

21 Gastric Pits and Gastric Glands Gastric Pits: shallow depressions of gastric mucosa Gastric Glands: –Open to gastric pits –Endocrine and exocrine cells in walls –Exocrine secretions gastric juice

22 Protects walls of stomach Acid environment activates pepsinogen Absoption o f B12 in small intestine Initiates protein breakdown Hormonal activity initiates smooth muscle action and secretion of gastric juice

23 What stimulates secretion of Gastrin?

24 Secretion of gastric juice – parasympathetic involvement – sensory stimuli

25 Small Intestine Three parts Digestive processes –Absorption of lipids Special adaptations – functions Support


27 Absorption in Small Intestine

28 Absorption of Lipids Bile salts act to emulsify Fatty acids + glycerol at villi –Intermediate metabolic conversions chylomicrons – protein encased structures enter blood stream –Delivered to tissues as LDL Liver as HDL –Bile salts feces

29 Where will the absorbed nutrients go?

30 Pancreas- Endocrine/Exocrine Endocrine – Islet tissues Exocrine – acinar cells via pancreatic duct ?? (where) –Pancreatic juice: Pancreatic amylase Trypsin Lipase etc. Releases bicarbonate ions – neutralizes chyme –Regulation via secretin from duodenal epithelial tissues Cholecystokinin


32 Liver Lobes divided into lobules Blood from portal vein sinusoids central canal Multiple functions –Blood glucose glycogen blood glucose –Lipid oxidation –Formation of urea from NH 2 –Deamination of aa –Storage –Production of bile


34 Bile and the Gall Bladder Bile –Bile salts –Others –Emulsification of lipids –Released as fatty substance enter lumen of duodenum –Cholecystokinin (CCK) stimulates contrations of gall bladder


36 Large Intestine Regions –Cecum Veriform appendix –Colon – 4 regions –Rectum –Anal canal Internal & external anal sphincters Functions

37 Symbiotic Bacteria Reside in the Colon Numbers- about 50 species. Fecal component- accounts for about 1/3 the total weight of feces. They are nourished by undigested foods. Their metabolic processes produce gas. Some produce vitamins B and K. They decompose pigmented molecules, which give feces its brown color.


39 Nutrition Macronutrients – energy source –Calorie – measure of energy in foods Micronutrients – required for vital biochemical processes –Incl. vitamins & minerals Hydrolysis – initial step

40 Essential nutrients Essential fatty acids –Required for synthesis of other forms in liver Linoleic acid Essential amino acids (8) –See table 15.8 Complete vs partially complete proteins

41 Issues with Fats and Cholesterol –4x amt of energy in carbs –Does Cholesterol intake greatly impact risk of heart disease? –What is the impact of intake of different kinds of fats on arthrosclerosis – (linked to heart disease)? –Trans fats?



44 Carbohydrates – all are not the same Glycemic Index: impact/rate of change in blood glucose levels after ingestion

45 Some examples of high vs. low glycemic index foods Impact of milling on glycemic index

46 Vitamins Fat soluble Water-soluble –B complex –C (ascorbic acid)

47 The End.

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